1. Field of the Invention
The present invention relates to portable terminals, including Personal Digital Assistants (PDAs), cellular phones, hand-held phones and smart phones. More particularly, the present invention relates to a cost-reduced keypad assembly mounted in a portable terminal.
2. Description of the Related Art
A common portable terminal represents a number of various portable devices that include a data input/output unit, a transmission/reception unit, an antenna device, a power supply device, etc. and by which a user can wirelessly communicate with the other party. In such a portable terminal, a keypad assembly is mainly used as a data input unit, a display unit is used as a data output device, and a touch screen is typically used as a data input/output device. The keypad assembly allows the user to input desired data by key pressing, and the touch screen with a touch sensitive panel enables the user to input desired data by screen touching and check the input data. A data input/output unit, which is one of the most important components in the portable terminal, is normally disposed on a front face of the terminal body to enable the user to read displayed data easily and to perform key manipulation.
Referring now to FIG. 1, a conventional portable terminal 100 has a body 10, on the front face of which a speaker device 12, a display unit 14, a keypad assembly 16 and a microphone device 15 are disposed in the order named. The speaker device 12 is typically arranged at an upper end of the body 10 and the microphone device 15 is arranged at a lower end, similar to a conventional telephone. A distance between the speaker device 12 and the microphone device 15 corresponds to an average ear-to-mouth distance of a user.
The display unit 14 is arranged at an upper side of the body 10 so that the user may easily watch the display unit 14, and the keypad assembly 16 is arranged at a lower side of the body 10, so that the user may easily manipulate keys, with one hand gripping the portable terminal. An external casing of a common portable terminal is realized by putting an upper casing C1 and a lower casing C2 together.
The display unit 14 has a display window 14a that preferably can be seen from the exterior, and the keypad assembly 16 has only the key tops 16a exposed to the outside for the user. The display window 14a is made of a transparent acrylic material to enable the user to read data displayed on the display unit 14, and the key tops 16a of the keypad assembly 16 are exposed from the surface of the portable terminal so that the user may input desired data by pressing selected key tops.
Referring now to FIG. 2, an assembly process of the conventional portable terminal includes coupling the keypad assembly 16 and the display window 14a, which were assembled into separate parts by independent assembly processes, in the upper casing C1 of the body 10. In general, the display window 14a is adhered to a proper place of the upper casing C1 along with an acrylic sheet using adhesive substances. In particular, the display window 14a is coupled with a lower side of the upper casing C1 along with a display unit or an undepicted touch sensitive panel.
Referring to FIGS. 2 and 3, metal domes 18 are formed on a single dome sheet Flexible Printed Circuit Board (FPCB) 18a, facing actuators 16b, with the dome sheet FPCB 18a adhered to a Printed Circuit Board (PCB) 17. Connectors 19 provided on the dome sheet FPCB 18a, as illustrated in FIG. 3, are connected to undepicted connectors on the PCB 17 to ensure a proper electrical signal connection.
In the structure shown in FIG. 1, if the user presses down any one of the key tops 16a, a relevant actuator 16b (shown in FIG. 2) on the keypad assembly 16 presses its associated metal dome 18 arranged on the PCB 17, thereby applying a signal. If the applied force is removed, the actuator 16b returns to its original location and the key top 16a also returns to its original position. The key tops 16a and the actuators 16b are made of silicon rubber to secure a desired elastic force.
As another example, even though an undepicted touch sensitive panel is provided on the portable terminal as a data input device, so as to take the place of the keypad assembly 16, wherein the touch sensitive panel and the display window 14a are assembled by independent assembly processes.
However, in the conventional portable terminal assembly process, the keypad assembly is independently assembled in the upper casing and the display window is also separately assembled in or attached to a proper place of the upper casing, causing an increase in manhour and thus reducing productivity. In addition, the key tops on the conventional keypad assembly should be assembled in keypad holes formed in the upper casing, reducing some steps and providing improved assembly (easier construction) as well.
Further, in the conventional assembly process, the dome sheet FPCB is attached onto the PCB and then connectors thereon are connected to undepicted connectors on the PCB, increasing the man-hours for assembly and thus causing a reduction in productivity.
In addition, the keypad assembly and the display window, which are assembled separately, are then assembled in the upper casing of the body, becoming an obstacle to an elegant external design of the portable terminal. That is, there is a limitation in providing a simple exterior design of the portable terminal.